1. Field of Invention
The present invention relates to a fan and an impeller thereof and, in particular, to a fan and an impeller thereof with rotation stability.
2. Related Art
Fans are now in widespread use for heat dissipation, and are typically driven by motors so as to rotate and produce a pressure gradient, thereby generating a fluid flow. Consequently, it is an essential requirement for the fans to provide a good rotation balance.
Referring to FIGS. 1 and 2, a conventional fan includes an impeller 1 and a motor (not shown) for driving the impeller 1. The impeller 1 includes a hub 11 and at least one blade 12 disposed around the hub 11. In a practical manufacture, the impeller 1 is a one-piece molding by injection molding to form the blades 12 and the hub 11, with at least one straight type balancing portion 110. Conventionally, a tool is used to properly put the balancing object B, which is commonly selected from a high viscosity material such as epoxy or clay, into the straight type balancing portion 110 of the hub 11 according to the result of the oscillation test for the rotation of the impeller 1. The balance of the rotation of the fan is thereby adjusted. However, while using the tool to put the balancing object B into the balancing portion 110, the balancing object B is not easily separated from the tool due to high viscosity of the balancing object B. This is inconvenient to users.
As shown in FIG. 2, when the fan is rotating, centrifugal acceleration causes the balance object B to be easily spilled out from the edge of the opening of the straight type balancing portion 110. Accordingly, the appearance of the fan is unclean, and the rotation balance and reliability of the fan are destroyed.
Therefore, it is an important subject of the invention to provide a fan and an impeller thereof for avoiding the balance object B being spilled out, and to improve the rotation stability of the fan. As a result, reliability and lifetime of the fan can be increased.